1. Field of the Invention
The present invention relates to modified rosins which are useful as binders in printing inks and coating compositions. More specifically, the present invention relates to phenolic-modified esters of rosins and their use in lithographic inks.
2. Brief Description of the Prior Art
Rosins have been generally disclosed for use as binders in inks. For this use, the desired properties of the modified rosins are, in the main, high softening point and good dilutability. Quite often, it has been found that one of these properties is improved at the expense of the other. The lack of this combination of properties in the modified rosins and other ink binders, for that matter, adversely affects the service requirements of inks as discussed hereinbelow.
Lithographic inks are used in printing processes that employ planographic plates to separate image from non-image area. The image areas are preferentially wet by ink, and the non-image areas are preferentially wet by water. During printing, the ink must remain sufficiently stable to transfer properly; yet the printed ink must rapidly dry to a solid.
Lithographic ink binders, which are of particular interest here, are selected on the basis that will ensure the above properties. For example, the working properties of the inks can be ensured by controlling the extent to which the ink, by virtue of its binder, and water interact to form a water-in-ink emulsion. The working and/or printing properties on the press at the prevailing press speed can be affected by this interaction. Generally, the ink must be sufficiently viscous in order to transfer without "flying-off". Yet, it must not be so tacky as to effect picking of the printed matter. Also, the printed ink must dry rapidly.
As can be seen from the foregoing, the selection or the preparation of ink ingredients, and in this case the ink binder, that will meet the above requirements is a difficult task. By this invention, one such type binder and inks formulated therewith are provided.